iPhone activation requires an iTunes Store account OR a major credit card, and a valid social security number, "as required by AT&T." (Apple touts the ability to activate the iPhone in iTunes in the comfort of your own home as opposed to standing around the AT&T Store as a plus, and I can certainly see that. You can also have the store do it.) Customers with existing AT&T accounts will have the option of keeping their existing phone number and upgrading their account.
All service plans include unlimited data, visual voicemail, 200 SMS text messages, rollover minutes, and unlimited mobile-to-mobile calling (presumably just to other AT&T Wireless customers). Plans are $59.99 for 450 minutes, $79.99 for 900 minutes, and $99.99 for 1,350 minutes per month, with a two-year agreement. There's a one-time activation fee of $36. Family plans are available, though details are not provided yet.
Dave Zatz raises the issue that these plans are actually quite inexpensive, compared to the $80/month he pays AT&T Wireless for voice and data on his Samsung Blackjack. He says two years of the lower-priced plans for the iPhone would nicely offset the steep initial hardware cost.